1. FIELD OF THE INVENTION
The invention relates to a continuously operating filtering device comprising a carrier belt movable round guide rollers and at least one drive roller and a filter belt supported thereby and means for supporting the carrier belt.
2. DESCRIPTION OF THE PRIOR ART
Such filtering devices, particularly when they are accommodated in a housing or casing, are voluminous which causes problems at the location of use, for instance in the processing industry.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to limit the size of the device.
This is achieved according to the invention in that the carrier belt is made of plastic.
By choosing a plastic carrier belt, the diameter of the drive roller and guide rollers can be kept considerably smaller than is the case with the usual rubber carrier belt. A limitation to 25% of the roller diameter in the case of rubber carrier belts is possible. It is of further advantage that plastic is generally resistant to aggressive substances, which is not the case with rubber.
In the case of a rubber carrier belt, lubrication has to be applied between the means for supporting the carrier belt and the carrier belt itself, since the coefficient of friction of the rubber material is comparatively high. Lubrication can be dispensed with when plastic is used.
As a result of the lower friction the driving power can likewise be limited.
The plastic can be a thermoplastic plastic. A thermosetting plastic may also be chosen. Thermoserring plastic is relatively stiff material. In order to enable training of the belt round the guide rollers, the belt must be constructed from connected links of limited length. Thermosetting plastic can be applied at high temperatures and is more resistant in a chemical atmosphere to for instance solvents.
The device can be accommodated in a housing and be provided with means for maintaining a desired pressure in the housing.
Such filtering devices can be used when for instance solvents can occur freely through evaporation and these gases must be held in a closed circuit. Due to the lower structure of the invention the total size of the filtering device can be restricted despite accommodation in the housing or casing.
At the beginning and end of the path traversed jointly by the carrier belt and the filter belt sealing means can be applied running in a transverse direction and in a lengthwise direction with respect to the belts.
Further advantages and features of the invention will become apparent from the accompanying claims and figure description.